Water in the gutter and down pipes after 3 days of rain

We are in a double storey house and as the title indicated water just started flowing through the down pipes in the lower level, there was not much rain since Friday in Melbourne and zero rain today. I checked the gutter in the ground floor roof and it seems the water is coming from the top floor. What would be the reason this? Should I be worried? My best guess would be something was blocking the gutter or down pipes and the blocking suddenly opened? I checked everywhere if there is leakage inside the house and found none.

 

Is the air conditioning working?

 

Just put that problem on your list for 3 months preventive maintenance schedule, as I think there may have been blockages in the downpipes as water only runs one way,unless under pressure..

 

I used food dye to check if my down pipes are flowing, start at the back and put a bucket of water with blue food dye down the pipe followed by the hose and then check to see how long (if at all) it takes to make it to the street.
I used other colours in the other downpipes and check them as well, that's how i found which pipe was blocked, Then i cut the pipe under the house where the 3 pipes joined together and flushed out the 25yrs worth of leaves and just and put another join in the pipe, so far, so good gutters don't overflow anymore.
Plus i removed the offending Jacaranda.

 

Could be your underground stormwater pipes are blocked.

 

Pressure relief valve failure ?

 

Air con drain. ACs can make litres a hour. To test turn off ona hot sunny day. Check it dries. Turn on. Check gutters are wet.
Poor gutter angles / blocked upper level downpipe although unlikley
Pool solar or solar hot water leak
Overnight rain ?
Where is the HWS ?

Are you sure which stormwater outlet is yours ? Not a neigbours is it ? My nieghbour thought my outlet was theirs as they barely evenr use their AC and we use ours a bit. To test block a grass level drain and then deluge it and see which outlet on gutter is impacted.

 

Thanks all for the ideas and suggestions. I realised the water started to flow immediately after turning on the AC. A plumber has come to have a look today and suggested not to worry about much as there was no dripping of water into the house. However the gutter definitely need cleaning and possibly the down pipes require replacing and re-adjustment considering they are too old and the previous owners made several unprofessional changes. I like the experiment with the dye suggested above. I myself did this and salt water dilution for measuring river flow in my previous professional career. I will take that in mind if I ever get such an issue.